THURSDAY, April 25 (HealthDay News) -- A belief in God may boost the effectiveness of short-term treatment for mental illness, according to a small new study.

The study included 159 psychiatric patients whose levels of depression, well-being and self-harm were assessed at the start and end of the study. The patients also were asked about their belief in God.

Patients with higher levels of belief in God were twice as likely to respond to treatment as those with no or little belief in God. Even among the more than 30 percent of patients who said they had no specific religious affiliation, those who had a moderate or high belief in God had a better response to treatment than those with little or no belief.

The study appears in the latest issue of the Journal of Affective Disorders.

"Our work suggests that people with a moderate to high level of belief in a higher power do significantly better in short-term psychiatric treatment than those without, regardless of their religious affiliation," study author David Rosmarin, a clinician at McLean Hospital in Belmont, Mass., and an instructor in the psychiatry department at Harvard Medical School, said in a hospital news release. "Belief was associated with not only improved psychological well-being, but decreases in depression and intention to self-harm."

A strong belief in God may boost patients' conviction that treatment will help them and their expectations of success, the researchers suggested.

Although the study found an association between belief in God and increased response to psychiatric treatment, it did not prove a cause-and-effect relationship.

"Given the prevalence of religious belief in the United States -- more than 90 percent of the population -- these findings are important in that they highlight the clinical implications of spiritual life," Rosmarin said. "I hope that this work will lead to larger studies and increased funding in order to help as many people as possible."